1. Field of the Invention
The present invention concerns a computed tomography (CT) system with a stationary anode ring, of the type known as fifth-generation computed tomography systems.
2. Description of the Prior Art
DE 10 2004 061 347 B3 discloses an example of a CT system of this type. This patent document describes a CT system of the fifth generation in which x-ray radiation is generated at a stationary anode ring with the use of a directed electron beam, which x-ray radiation is pre-filtered with the aid of a bowtie filter and collimators and strikes an oppositely situated detector, likewise mounted on a support frame. The support frame is continuously aligned with the rotating x-ray focus that is generated by the electron beam, so that the x-ray fan that is emitted always passes in the same way through the filter mounted on the support frame and strikes the detector.
Such a CT system is very complicated in design since the electron beam that is generated requires a complex deflection device in order to align it appropriately on the anode ring. Furthermore, spatial problems occur in such a CT system since the electron beam emitter must be arranged in the region of the system axis. The free displacement capability of a patient bed or subject table is severely hindered by this arrangement. An even higher cost expenditure is required if the electron source is placed elsewhere, in order to concentrate the electron beam over a significantly longer distance and direct it to the anode. The use of a stationary detector covering 270° to 360°, as is typical in fifth-generation CT systems, is also very complicated.
Third generation CT systems also are known wherein an x-ray tube is mounted on a rotating gantry or support frame. This requires a support frame with very complicated bearing in order to handle the centrifugal forces that arise due to the rotation of x-ray tube. Furthermore, in such an embodiment of a CT system it is necessary to supply high voltage to the x-ray tube via costly slip rings.
United States Patent Application Publication No. 2006/0002514 A1 and EP 0 377 070 A1 describe further examples of such known CT systems.